BFO 2 Reference: To say that b is causally unified means: b is a material entity which is such that its material parts are tied together in such a way that, in environments typical for entities of the type in question,if c, a continuant part of b that is in the interior of b at t, is larger than a certain threshold size (which will be determined differently from case to case, depending on factors such as porosity of external cover) and is moved in space to be at t at a location on the exterior of the spatial region that had been occupied by b at t, then either b’s other parts will be moved in coordinated fashion or b will be damaged (be affected, for example, by breakage or tearing) in the interval between t and t.causal changes in one part of b can have consequences for other parts of b without the mediation of any entity that lies on the exterior of b. Material entities with no proper material parts would satisfy these conditions trivially. Candidate examples of types of causal unity for material entities of more complex sorts are as follows (this is not intended to be an exhaustive list):CU1: Causal unity via physical coveringHere the parts in the interior of the unified entity are combined together causally through a common membrane or other physical covering\. The latter points outwards toward and may serve a protective function in relation to what lies on the exterior of the entity [13, 47

BFO 2 Reference: BFO rests on the presupposition that at multiple micro-, meso- and macroscopic scales reality exhibits certain stable, spatially separated or separable material units, combined or combinable into aggregates of various sorts (for example organisms into what are called ‘populations’). Such units play a central role in almost all domains of natural science from particle physics to cosmology. Many scientific laws govern the units in question, employing general terms (such as ‘molecule’ or ‘planet’) referring to the types and subtypes of units, and also to the types and subtypes of the processes through which such units develop and interact. The division of reality into such natural units is at the heart of biological science, as also is the fact that these units may form higher-level units (as cells form multicellular organisms) and that they may also form aggregates of units, for example as cells form portions of tissue and organs form families, herds, breeds, species, and so on. At the same time, the division of certain portions of reality into engineered units (manufactured artifacts) is the basis of modern industrial technology, which rests on the distributed mass production of engineered parts through division of labor and on their assembly into larger, compound units such as cars and laptops. The division of portions of reality into units is one starting point for the phenomenon of counting.

BFO 2 Reference: Each object is such that there are entities of which we can assert unproblematically that they lie in its interior, and other entities of which we can assert unproblematically that they lie in its exterior. This may not be so for entities lying at or near the boundary between the interior and exterior. This means that two objects – for example the two cells depicted in Figure 3 – may be such that there are material entities crossing their boundaries which belong determinately to neither cell. Something similar obtains in certain cases of conjoined twins (see below).

b is an object means: b is a material entity which manifests causal unity of one or other of the types CUn listed above & is of a type (a material universal) instances of which are maximal relative to this criterion of causal unity. (axiom label in BFO2 Reference: [024-001])